Differential pressure transducer



5 Sheets-Sheet 1 R E z m m I a n w 1 V1 H 0 Y Z L B W wfii 2 m Mun Aug. 24, 1965 H. c. BECK DIFFERENTIAL PRESSURE TRANSDUCER Filed July 27, 1962 4/ J w W Aug. 24, 1965 H. c. BECK 3,201,989

DIFFERENTIAL PRES SURE TRANSDUCER Filed July 27, 1962 5 Sheets-Sheet 2 INVENTOR flame) 6. 350 4 r 4? JM Aug. 24, 1965 c, BECK 3,201,989

DIFFERENTIAL PRESSURE TRANSDUCER Filed July 27, 1962 5 Sheets-Sheet 3 li my;

INVENTOR. fle/vev 6. 5

gw 5M United States Patent Navy Filed July 27, 19:32, Ser. No. 213,067 8 Claims. (Ci. 73-39%) This invention relates to differential pressure transducers and especially to a deep-sea, differential pressure transducer which is extremely accurate at high pressures.

In oceanographic work, it is often necessary to measure small changes in depth and/ or small changes in depth from a reference depth. A conventional method employed for this purpose is to measure hydrostatic presstitutes another example of this type of medium.

The accuracy of most commercially available pressure transducers is expressed as a percentage of the range of the instrument. Thus, the accuracy of high-pressure transducers for small changes in pressure is poor. The present invention permits the use of a limited-range differential pressure transducer to measure small pressure differences in a high-pressure environment thereby taking advantage of the high accuracy inherent in a low-range instrument.

A typical embodiment of the present invention utilizes a differential piston opposed by a spring to drive an adjustable valve which closes one port of a low-range differential pressure transducer at a pre-determined point of high pressure. A second port of the differential pressure transducer is always exposed to the ambient environment (sea water) so that diiferences between the ambient pressure and the predetermined pressure are measured.

An object of this invention is to accurately measure small differences in pressure at high average pressure levels.

Another object is to accurately measure small differences in pressure at great depths in an oceanic environment.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of an embodiment of the invention taken along the line 11 in FIG. 2;

FIG. 2 is an end view of the embodiment shown in cross-section in FIG. 1;

FIG. 3, is a fragmentary cross section taken along the line 3-3 in FIG. 2 and shows details of the seal through which leads are brought out of the device; and

FIG. 4 is a cross-sectional view of another embodiment of the invention.

FIG. 1 illustrates an embodiment of the invention which is divided into two basic parts consisting of pressure transducer means which is responsive to difleren- 'tial pressure and piston means for providing a reference 3,201,989 Patented Aug. 24,1965

28 in the casing of the gauge chamber 12 and another opening (the reference inlet) 30 which is coupled to an opening (the reference port) 32 in the second chamber (the diaphragm chamber) 14.

The casing of the diaphragm chamber 14 encloses a molded diaphragm 34, the space between the molded diaphragm 34 and the gauge chamber 12 being fluidtight. This diaphragm 34 is made of synthetic rubber and is collapsible. A valve port 36 provides a passageway through the partition 38 which separates the diaphragm chamber 14 from the open piston chamber 16.

The piston means comprises an open piston chamber 16, a closed piston chamber 18, a piston rod 44, a piston spring 52 and a ruler 50. The open piston chamber 16 is open to the influx of the surrounding environment. Its casing consists of four rod-like members 40 (two being shown in FIG. 1) which are welded or otherwise bonded at one end to the partition 38 and at the other end to a flange 42. The purpose of the rod-like members 4() is to support the closed piston chamber 18 and the piston members; fewer members 40 can be employed if they furnish suflicient support.

The piston rod 44 extends through the open 16 and the closed 18 piston chambers and has an exteriorly threaded end 46 in the open chamber 18. An interiorly threaded valve cylinder 47 is screwed on the threaded end 46 of the piston rod 44. The valve cylinder 47 bears a valve plug 48 at the end of the cylinder 47 closest to the valve port 36. A cylindrical piston spring 52 extends between a flange 56 on the piston rod 44 and the opposite transverse wall 54 of the closed piston chamber 18. A ruler 5%) which extends along the direction of the piston-rod axis is located within the open piston chamber 16.

The operation of the device is as follows:

The pressure transducer, or gauge, 22 has as its active element a diaphragm which, when deflected, moves a coil which varies the reluctance of an electrical circuit which, in turn, varies the frequency of an electrical signal. There is an air chamber on one side of the diaphragm, the reference opening 30 being coupled therewith. The other side of the diaphragm is exposed to the ambient environmentv(sea water) through the ambient opening 24, connecting tubing and the ambient port 28.

As the device is lowered into the sea, the water exerts increasing pressure upon the ambient side of the diaphragm and equal pressure upon the collapsible diaphragm 34, since the water has access to the latter through the open piston chamber 16 and the valve port 36. The collapsible diaphragm 34 shrinks in size, thereby correspondingly increasing the air pressure in the airchamber side of the gauge diaphragm.

This pressure increases until the valve plug 48, which has been moving towards the valve, or reference, port 36, as the piston is forced inward by pressure of the sea water against its end face 58, is fully seated in the valve port 36. The seating of the valve plug 48 traps the water which is within the diaphragm chamber and prevents any further influx of water, thereby preventing any further increase of pressure against the collapsible diaphragm 34 and hence against the air-chamber side of the transducer diaphragm.

This reference pressure (the pressure existing when the valve port 36 is closed) is determined by the distance between the valve port 36 and the valve plug 48 and is preset by screw adjustment between the valve-plug cylinder and the threaded end of the piston. After the valve preset reference pressure affects the. electrical signal by moving.'theltransducerdiaphragm, the frequency of the signal indicating the difierence in depth between the reference depth and the depth of th'e dev ice. p

of. the devicestillincreases The pressure transducer may, fo rfexarnple, befan' Ultradynemodel 8-90-TA-100 which is able to rneas-i ure difierential'pregssures up. to 100;p.s.i. I I

The device is madefluidtight at the necessary, points by means ofrubber fQ-rings The; metal employed is stainless steel, a metal which has strength and anti-cor rosion properties: s

An end viewof the devic etis shown inIFI G, The

device has anend seal 62 through whichtwoelectrical cables 64 are broughtin. Afragmented cross-sectionof the end seal 62 and end plate 66 of the gaug cha b r 12 is shown inFIQ 3,. a

FIG. 4 illustrates an embodiment which employs a pressure gauge 22" in which'r both sides'ofthe gauge diaphragm can be exposed ;to sea water. In this'case,.the

collapsible diaphragm- 34 and the diaphragm chamber 14 of FIG. 1 are unnecessaryand the reference port also functions as the valvejport. 'The combined reference and valve port is'denoted by numeral 32,. Theunit is otherwise similar to that in FIGLjl, ,7 Obviously many modifications'and variations of the presentinvention are possible inthe light 'of the above teachings; It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim: a

1. A depth-measuring device comprising, in combination:

. transducer means including a casing formed with an ambient port and a reference port both coupled t 4: the ambient pressure by being coupled with said ambient port and the other said pressure-gauge opening being exposed to the pressure in said diaphragm chamber by being coupled with-said reference portrand 7 I piston means comprising a piston chamber afiixedlto said diaphragm chamber,one section of said'piston chamber being fluidtight and the other section being open to the ambient medium, said other section being located 7 adjacent to said valve port,

a piston rod having a threaded-end, said piston rodabeing locatedin the open section of the pistonchamber;

cylindrical body and a valve plug afi'ixed at one end thereof, said body being screwable upon the threaded end of said'pistori rod, and said plug being'shaped to close off said valve port when seated therein by axialmovement of said piston rod, 1 a a I a spring located within the closed section of said piston chamber and acting upon said piston rod to opposethe ambient pressure which forces said pistonrod in sucha direction as to seat said valveplug in said v valve port, thereby establishing arefer'en'ce pressure within said diaphragm chamber-at the pressure at whi'ch said seating 4. A device as set'forth'in. c1ainr3, further including a ruler located 'within said open section of said piston chamber and arranged parallel to said piston rod whereby 'the original distance of said valve plug from said .valve with the ambientenvironinent iand.pressure-gauge* v means havingtwo openings and being responsive to V the difference in pressure at said'two openings, one said opening being coupled pressurewise with said ambient port and the other saidopening being coupled pressurewise with said reference'port; and

piston'means including ar-piston 'rodyme'ans movable alongvone end of said piston rod' and a valve plug af fixed 'to'one end, of said movable means, 7 7

said piston rod moving ,a 3 distance corresponding to f the ambient pressure and acting to seat said valve plug in said reference portata predetermined am-f' bient pressure when saidipis ton rod has moved-a predetermined distance, thereby closing off said refer:

ence port and fixing a reference pressure level 'at the reference. opening 'of said pressure-gauge r'n'eans. 2. A device as 'setlforth in claim 1, further including a ruler arranged parallel to said piston rod whereby the be set accurately.

tion: v u

transducer means comprising a fluidtight gauge chamber formed withanarnbient a diaphragm chamber affixed to reference port 7 .end of said gauge-chamber, said "diaphragm chamber being formed Witha valve'port'therein', i V 70. j i:

and a collapsible fluidtight diaphragm within said diaphragm chamber, said diaphrag m being situated between said referencepo'rt andsaid" distance'of said valve plug 'frorn said reference port can 3. A depth-measuring device comprising, in coiribinavalve port so thatthe reference'port side of the;

diaphragm chamber;"made fluidtightp one said pressure-gauge opening beingexposed f0 w an electrical signal having a frequencyrw'hich is proportional to the ditference in pressure is measured, by said differential pressure gauge.

6. A depth-measuring device" comprising, in combination:'*i i I V transducer means comprising t a fiuidtight' gauge chamber formed with an ambient port and a valve port, a differential pressure gauge having two openings 7 for the application of. pressure thereto, the difference of 'saidpressures being measured by said a e, 1 I one said pressure-gauge opening being, exposed to the ambient pressure by being coupled with a said ambient port and the otherv said pressuregau'ge opening ibeing exposedto the ambient pressure by being coupled with said valve'port;

piston mean's comprising 1 V apiston chamber affixed to said gauge chamber,

one section of said piston chamber being fluidtight and theother section being open to the am- *b'ient medium, s'aidotherseetion being located adjacent 'tosa'idvalve port,- r 1 a piston rod" having a threaded end, said piston rod'beinglocated'in the open section of the pisl n ch m a a valve hiein-ber havihg an internally threaded cylindricalbody and a valve plug affixed at one end'ther'eof, said body being screwable upon the threaded end of said piston rod, and saidplug being shaped to close off said valve portw'hen f 's'e'atedther'ein by axial movement :of "said piston rod, aiidr piston chamber and, acting uponsaid rod to oppose the a mbient pressure which forces said piston 'rod' insuch a direction as to seat said valve i a valve member having an internally threaded star ng located' within the closed section of said 3,201,989 5 6 reference pressure at the pressure-gauge openis proportional to the diflerence in pressure which is ing which is coupled with said valve port, said measured by said diiferential pressure gauge. reference being the ambient pressure at which said seating occurs. References Cited by the Examiner 7. A device as set forth-in claim 6, further including 5 UNITED STATES PATENTS a ruler located within said open section of said piston chamber and arranged parallel to said piston rod wherefix gs; by the original distance of said valve plug from said valve port can be set accurately. FOREIGN PATENTS 8. A device as set forth in claim 6, further including 10 1,0 4 711 7 54 France. electronic means located within said gauge chamber for producing an electrical signal having a frequency which S AC ANN, ary Examiner. 

3. A DEPT-MEASURING DEVICE COMPRISING, IN COMBINATION: TRANSDUCER MEANS COMPRISING A FLUIDTIGHT GAUGE CHAMBER FORMED WITH AN AMBIENT PORT AND A REFERENCE PORT, A DIFFERENTIAL PRESSURE GAUGE HAVING TWO OPENINGS FOR THE APPLICATION OF PRESSURE THERETO, THE DIFFERENCE TO SAID PRESSURES BEING MEASURED BY SAID GAUGE, A DIAPHRAGM CHAMBER AFFIXED TO THE REFERENCE PORT END OF SAID GAUGE CHAMBER, SAID DIAPHRAGM CHAMBER BEING FORMED WITH A VALVE PORT THEREIN, AND A COLLAPSIBLE FLUIDTIGHT DIAPHRAGM WITHIN SAID DIAPHRAGM CHAMBER, SAID DIAPHRAGM BEING SITUATED BETWEEN SAID REFERENCE PORT AND SAID VALVE PORT SO THAT THE REFERENCE PORT SIDE OF THE DIAPHRAGM CHAMBER IS MADE FLUDTIGHT ONE SAID PRESSURE-GAUGE OPENING BEING EXPOSED TO THE AMBIENT PRESSURE BY BEING COUPLED WITH SAID AMBIENT PORT AND THE OTHER SAID PRESSURE-GAUGE OPENING BEING EXPOSED TO THE PRESSURE IN SAID DIAPHRAGM CHAMBER BY BEING COUPLED WITH SAID REFERENCE PORT; AND PISTON MEANS COMPRISING A PISTON CHAMBER AFFIXED TO SAID DIAPHRAGM CHAMBER, ONE SECTION OF SAID PISTON CHAMBER BEING FLUIDTIGHT AND THE OTHER SECTION BEING OPEN TO THE AMBIENT MEDIUM, SAID OTHER SECTION BEING LOCATED ADJACENT TO SAID VALVE PORT, A PISTON ROD HAVING A THREADED END, SAID PISTON ROD BEING LOCATED IN THE OPEN SECTION OF THE PISTION CHAMBER, A VALVE MEMBER HAVING AN INTERNALLY THREADED CYLINDRICAL BODY AND A VALVE PLUT AFFIXED AT ONE END THEREOF, SAID BODY BEING SCREWABLE UPON THE THREADED END OF SAID PISTON ROD, AND SAID PLUG BEING SHAPED TO CLOSE OFF ALL VALVE PORT WHEN SEATED THEREIN BY AXIAL MOVEMENT OF SAID PISTON ROD, A SPRING LOCATED WITHIN THE CLOSED SECTION OF SAID PISTON CHAMBER AND ACTING UPON SAID PISTON ROD TO OPPOSE THE AMBIENT PRESSURE WHICH FORCES SAID PISTON ROD IN SUCH A DIRECTION AS TO SEAT SAID VALVE PLUG IN SAID VALVE PORT, THEREBY ESTABLISHING A REFERENCE PRESSURE WITHIN SAID DIAPHRAGM CHAMBER AT THE PRESSURE AT WHICH SAID SEATING OCCURS. 